Apparatus for heating metal objects



Sept. 22, 1942- R. E. BUCKHOLDT APPARATUS FOR HEATING METAL OBJECTSFiled May 28, 1940 3 Sheets-Sheet l a? Snnentor R0 BERT. E. BUCKHOLDT ZGttorneg Sept. 22, 1942- R. E. BUCKHOLDT APPARATUS FOR HEATING METALOBJECTS Filed May 28, 1940 5 Sheets-Sheet 2 Bnve ntm:

ROBERT E-BL|CKHO LDT Z @Z/VW (Ittorneg l &:

Sept. 22, 1942. R. E. BUCKHOLDT 2,296,306

APPARATUS FOR HEATING METAL OBJECTS Filed May 28, 1940 3 Sheets-Sheet 3I'mnenfor ROBERT E- EiucKHoLDT Patented Sept. 22, 1942 2,296,806APPARATUS FOR HEATING METAL OBJECTS Robert E Buckholdt, Salem, Ohio,assignor to Salem Engineering Company, Salem, Ohio, a

proprietorship Application May 28, 1940, Serial No. 337,604

9 Claims.

This invention relates to apparatus for heating metal objects and isparticularly concerned with the heating of objects, which are of greatlyvarying lengths, in a continuous but economical manner. The principlesof the invention are particularly applicable in the heat treating ofelongated metallic shapes but it should become apparent that, as thedisclosure thereof proceeds, the principles are applicable to otherspecific uses.

Heretofore the uniform and expeditious heating of large tonnages ofelongated metal shapes has been accompanied by considerable difficultydue principally to the difficulty of handling the long shapes andmaintaining a uniform and controlled heating rate or temperaturethroughout their entire extent. Such objects, which may comprise beamsor sections of various shapes, or tubes, may attain a length of onehundred feet or more and if a continuous furnace of conventional designwere employed the length thereof required to effect the proper timetemperature relation would be such as to be impractical. It isaccordingly the primary object of the invention to provide in a heatingfurnace an improved arrangement for supporting and moving the objectsthrough the heating zone of the furnace in a uniform and controlledmanner but which nevertheless is operative to uniformly heat all of theobjects positioned therein throughout their entire extent regardless ofthe shape or length of the objects.

A further object of the invention is the provision in a material heatingfurnace of an improved arrangement for directing the heat transferringfluid onto objects of varying and long lengths which are positioned inand moved through the heating chamber of the furnace whereby the objectswill be uniformly and expeditiously heated throughout their entireextent.

Another object of the invention is the provision of an improvedapparatus for heating elongated metal shapes and consists essentially inapparatus for moving the shapes sideways through the heating chamber ofa furnace and for applying a distributed flow of convection heatingfluids at locations spaced longitudinally along the objects, thetemperature of the fluid being uniformly controlled along thelongitudinal axes of the objects.

Yet another object of the invention is the provision of an improvedapparatus for uniformly heating objects of varying and long lengthswhich consists essentially in apparatus for moving the objects sidewaysthrough the heating chamber of a furnace and for applying a turbulentflow of convection heating fluids to said objects at locations spacedlongitudinally along said objects, the

direction of flow of said fluids over and about said objects beingopposite to the direction of movement of the objects through thechamber.

These and other objects and advantages of the invention will becomeapparent from a consideration of the following detailed specificationand the accompanying drawings wherein there is specifically disclosed apreferred embodiment of the invention.

In the drawings:

Figure 1 is a longitudinal sectional view of the material heatingfurnace of the invention, the view being taken along the line II ofFigure 2; Figure 2 is a plan view, partly in horizontal section, of theapparatus of Figure 1; and

Figure 3 is an enlarged view of the furnace hearth operated mechanism.

In the drawings the relative length of the furnace is greatly decreasedfor better exposition as in actual practice the length of the furnacemay be five or six times its width. The furnace consists essentially ofa casing Ill which, in accordance with usual practice, may be built upof structural and insulating brick being confined within the buckstaysII. The heating chamber l2 as well as all passages for the convectionheating fluids employed is preferably lined, as at l3, with chrome alloysheets which feature is of particular utility in the heating of softmetals, such as aluminum, as it eliminates any scoring and erosion ofthe surfaces of such objects.

Heating chamber l2 extends the entire length of the furnace casing andconvection heating fluid is supplied thereto by a series of heatingunits, indicated generally by the reference numeral l4, evenly spacedalong the top of the easing Ill. The heating units it each consist of achamber 15 in which is preferably positioned a number of electricalresistance heating units [6 although it should be understood that anyequivalent' heating means, such as liquid or gaseous fuel burners, maybe mployed for the purpose. Chambers l5 discharge into the materialheating chamber through the vertical ducts i'l extending down along oneend wall of the casing in and the heating fluid is withdrawn from thechamber l2 into the chambers l5 through ducts I8 positioned adjacent theopposite end wall of the furnace by the motor driven circulators 19, oneof which is provided for each of the heating units. The upper and lowerwalls of the heating chamber I2 are of saw tooth, formation, as shown at2i and 22, respectively, with the ribs running longitudinally of thefurnace. The ridges 23 of the upper wall are directly above the valleys24 34 arranged in pairs opposite each other.

of the lower wall to provide in effect a sinous passage for theconvection heating fluids transversely of the chamber. This results in asinous and turbulent flow of the heating fluids over and about thobjects passing through the chamber and materially aids intthe efficientand uniform transfer of heat from the fluid to the objects.

The object to be heated which may comprise metal beams, angles, tubesand so forth of varying lengths, are moved into and out of the furnaceand through the heating chamber thereof by the mechanism now to bedescribed. Extending on either side of the furnace and substantiallythroughout the entire length thereof are the shafts 30 which arejournaled in suitably fixed pillow blocks 3| and one of the shafts isarranged to be rotated at a uniform controlled rate of speed by themotor 32 through a speed reducing transmission 33. Keyed to the shafts30 at evenly spaced points are the sprocket wheels Entrained over thesprocket wheels of each pair is a continuous hearth chain 35, the upperreach of which passes through the heating chamber l2 and being operativeto support and propel the objects through the chamber, and the lowerreach passing below the bottom wall of the heating chamber.

Extending in parallel and horizontally spaced relation at each side ofthe furnace are the beams 31, the inner one being supported from thebuckstays II and the outer one by suitable columns 38. Spanning thebeams 31 at uniformly spaced intervals are the shafts 39 each of whichrotatably carries a member 40 having a bore of substantial length toreceive the shaft 39, an upstanding arm 4| and a pair of dependingbearing supports 42. Journaled in the supports 42 of each of the members40 is a shaft 43 which extends into the furnace heating chamber throughvertically elongated apertures 44 in the end walls of the furnace. Keyedto the inner end of each of the shafts 43 is a roll 45 having annularend flanges, as shown. A sprocket wheel 45 is keyed to the outer end ofeach of the shafts 43 and a chain 41 interconnects each of the wheels 46with a sprocket assembly 48 rotatably mounted on the associated shaft39. Each of the sprocket assemblies 48 on either end of the furnace isconnected together by a continuous chain 56 so that all of the rolls 45at either side of the furnace will rotate in unison. One of theassemblies 48 on each end of the furnace is driven by a motor 52 throughchain and speed reducing transmission 53.

By referring to Figures 2 and 3, it will be apparent that the inner endsof the shafts 43 and the rolls 45 are positioned intermediate the hearthchains 35. Shafts 43 and consequently rolls 45 are adapted to be raisedand lowered by pivotal movement of the members 46 about the shafts 39and the extent of this movement is such that the upper surfaces of therolls 45 may be moved from a position below the supporting plane of thechains 35 to a position thereabove and vice versa. To accomplish thispurpos the upper ends of the arms 4| of the members 40 along each sideof the furnace are pivotally connected to an elongated operating rod 54.The rods 54 are each connected to a piston of an air cylinder 55, whichcylinders are independently controlled by suitable valve means, notshown.

In operation the beams or other objects to be heated are moved into thefurnace on the conveyor 56 (Figure 2), which may be a motor driven rolltable extending from a rolling mill orother equipment of the plant. Byadmitting fluid pressure to the right side of the cylinder 55 at thecharging end of the furnace, as viewed in Figure 2, the rod 54 will bemoved to the left and the rolls 45 along the charging end of the furnacewill all be raised above the supporting plane of the hearth chains 35.This upper position of the rolls 45 is substantially in horizontalalignment with the conveyor 56 so that the pieces moving into thefurnace on the conveyor 56 will be directed onto the rolls 45. All'ofthe rolls are normally continuously driven by the motors 52bit a uniformrate of speed, which rate of speed is such that the peripheral velocityof the rolls 45 is substantially equal to the peripheral velocity of thedriven rolls of the conveyor 56. The pieces are retained on the elevatedrolls 45 by the end flanges of th rolls. As the piece approaches itsproper position in the furnace, air is admitted to the left side of thecylinder 55 at the charging end of the furnace and consequently theadjacent rolls 45 are moved below the supporting plane of the chains 35.This deposits the piece on the hearth chains and these, being moved at aconstant predetermined rate of speed by the motor 32, will move thepiece through the heating chamber of the furnace.

As indicated in Figure 1 of the drawings, the direction of materialtravel through the heating chamber of the furnace is opposite to thedirection of flow of the convection heating fluid therethrough. Byproviding a saw tooth configuration to the top and bottom walls of theheating chamber, substantially as shown, the convection heating fluidwill be caused to move through the chamber along a turbulent and sinuouspath of travel, thereby uniformly applying heat to all the surfaces ofthe beams or other pieces being heated. A temperature responsive element58 is located adjacent the exit end of each of the fluid heatingchambers l5 and through the medium of conventional control apparatus,not shown, control the operation of the respective heating elements l6.Thus the fluid coming into contact with the objects being heated at thedischarge side of the furnace is of accurately controlled temperatureand therefore the final temperature given the objects may be accuratelycontrolled. 7

' As the objects which have moved through the heating chamber reach aposition above the lowered rolls 45 along the discharge side of thefurnace, these rolls are all elevated by admitting air to the proper endof the cylinder 55 of the discharge side of the fumace'and, as the rolls45 are raised, they will support the objects free of the chains 35. Therolls 45, being continuously driven by the adjacent motor 52, will pro,

pel the objects out of the furnace onto the discharge conveyor 65 whichmay lead to quenching equipment or other station in the plant. Ifdesired, suitable mechanism, responsive to the advanced position of theobjects, may be pro vided to admit air to the proper side of thecylinder 55 at the discharge end of the furnace to automatically raisethe rotating discharge rolls 45 when the objects have reached a positionthereabove. Also, it should be apparent that automatic means may beprovided to lower the charging rolls 45 so that the furnace may bearranged for entirely automatic operation.

An important advantage of the apparatus of the applicant's invention isthat the objects to be heated, regardless of their length, may be veryrapidly moved into and out of the heating chamber of the furnace,thereby enabling the heating to be started along the entire extent ofthe objects at the same time and insuring a final uniform temperaturethroughout the objects. This minimizes the distortion of the shapedobjects and is of particular advantage in hardening operations. Also,ment enables these desirable results to be accomplished while usingapparatus of economical design and practical size and, by enabling thematerial charging and discharging ports to be kept relatively small, agood overall efficiency may be maintained.

It should be observed that the furnace of this invention is uniformlyoperative, regardless of the length of the objects to be heated. This isaccomplished in part by spacing the chains 35 and the rolls 45 at shortintervals so that short pieces may be adequately supported. In arepresentative installation of the furnace which has a hearth length ofone hundred and three feet and a width of eight feet the chains androllers are positioned on two feet centers. In this furnace sevenheating units, as described above, were employed and it was found thatthe temperature of the heating fluid was very uniform throughout theentire length of the hearth and it should therefore be obvious thatshort stock lengths will be uniformly heated, regardless of theirparticular location on the hearth. The furnace may thus be employed toheat miscellaneous shapes of varying lengths to a maximum substantiallyequal to the length of the hearth and, when shorter pieces are to becharged, these may be charged in groups having a combined length ofsimilar proportions. The furnace is so constructed and normally operatedthat the length of time each individual piece remains in the heatingchamber is the same and it is therefore possible to arrrange theapparatus for efficient automatic operation. The temperatures maintainedat the thermocouples 58, the speed of movement of the chains 35 androtation of the rolls 45 may be controlled at will to effect a properbalance between the various factors involved.

The above specifically described embodiment of the invention should beconsidered as illustrative only as obviously many changes may be madetherein without departing from the spirit or scope of the invention. Forexample, other means than that specifically disclosed may be employed todistribute the convection heating fluid over the objects to be heatedand various mechanical changes may be made in the object handling andmoving means. Reference should the arrangetherefore be had to thesubjoined claims in de- I termining the scope of the invention.

What I claim is:

1. Apparatus of the character described comprising in combination acasing having a heating chamber therein, means to circulate convectionheating fluid through said chamber, means to move objects to be heatedlongitudinally into one end of said chamber along one side thereof,comprising a series of driven rolls, means to raise and lower the axesof rotation of said rolls, a series of movable hearth chains spanningsaid chamber and positioned in part intermediate said rolls wherebyobjects to be heated coming into said chamber on said rolls will bedeposited on said chains when said rolls are lowered, a second similarseries of rolls positioned intermediate the chains at the opposite endof said chamber along the other side thereof and operative to propel theobjects out of the chamber, the axes of rotation of said rolls beingsubstantially paralleLvvith the direction of movement of said chains.

2. Apparatus of the character described comprising in combination a.casing having a heating chamber therein, means to circulate convectionheating fluid through said chamber, means to move elongated objects tobe heated into one end of said chamber along one side thereof comprisinga series of driven supported rolls, said rolls being carried by theinner ends of shafts extending from outside of to within said casing andchamber and journaled at their outer ends in pivotally mounted membersadapted to move about axes parallel with the axes of rotation of saidshafts, means mechanically connecting each of said members whereby saidmembers will be moved and said rolls raised and lowered in unison, meansto move said objects laterally through said chamber, the arrangement ofthe parts being such that when said rolls are lowered objects positionedthereon will be deposited on said laterally movable means, and means atthe other end of said chamber along the other side thereof to supportand move the objects longitudinally out of said chamber after they havetraveled through said chamber.

3. Apparatus of the character described comprising in combination acasing having a heating chamber therein, means to supply convectionheating fluid to said chamber and to circulate said fluid therethrough,means to move elongated metal shapes longitudinally into one end of saidchamber along one side thereof comprising a series of driven rollsextending along one side of said chamber, means in said chamber to movethe objects laterally through said chamber, means to raise and lowersaid rolls, the arrangement of the parts being such that as said rollsare lowered the objects supported thereon will be deposited on saidlaterally movable means, and means at the opposite side of said chamberto move said objects longitudinally out of said chamber along saidopposite side thereof.

4. Apparatus of the character described comprising in combination acasing having a heating chamber therein, means to move elongated metalobjects to be heated longitudinally into one end of said chamber alongone side thereof, means to move the objects laterally through saidchamber, means at the other side of said chamber to move the objectslongitudinally out of said chamber, and a plurality of heating unitspositioned above said chamber and evenly spaced along the transverseaxis of the laterally moving means; each of said units comprising aconvection heating fluid moving means, a convection fluid heating means,a fluid discharge outlet adjacent the last mentioned side of saidchamber, and a fluid return duct adjacent the first mentioned end ofsaid chamber.

5. Apparatus of the character described comprising a casing having aheating chamber therein, means to move elongated metal shapedlongitudinally into one end of said chamber along one side thereofcomprising a plurality of parallel shafts extending from outside of towithin the said one side of said chamber and each carrying at its innerend an object supporting roll, said shafts being disposed substantiallyat right angles to the direction of movement of the shapes into saidchamber, means to rotate said shafts in unison, means to move saidelongated shapes laterally through said chamber, means to move wherebysaid rolls may be simultaneously moved below the supporting plane ofsaid laterally moving means, and meansatthe other side of said chamberto move said elongated shapeslongitudinally out of said chamber.

6. Apparatus of the character described comprising a heating chamber, amovable hearth in said chamber, means to move elongated metal shapeslongitudinally onto one end of said hearth comprising a plurality ofspaced parallel shafts positioned outside of said chamber, a memberpivoteddintermediate its end on each of said shafts, a shaft journaledin one end of each of said members and extending into said chamber, asupporting roll keyed on the inner end of each of said last mentionedshafts and a sprocket keyed on the same shaft, a. sprocket rotatablymounted on each of said first mentioned shafts, means to rotate eachof-said sprockets in unison, means to mechanically connect the otherends of said member with a moving means whereby said members may berocked and their supported roll carrying shafts raised and lowered, andmeans to move the elongated shapes longitudinally away from the otherend of said hearth.

7. Apparatus of the character described comprising in combination acasing having a heating chamber therein, means to circulate convectionheating fluid through said chamber, a continuously moving hearthoperative to move objects from one side of said chamber to the otherside 2,296,808 the axes of rotation of said shafts in'unison thereof,means to move elongated objects to be heated longitudinally into saidchamber and to deposit the same. onto said hearth along one side of saidchamber, and means to raise said objects from said hearth and to movethe obthe other side thereof.

8. Apparatus of the character described comprising in combination acasing having a heating chamber therein, means to circulate convectionheating fluid through said chamber, a continuously moving hearthoperative to move objects from one side of said chamber to the otherside thereof, means to move elongated objects to be heatedlongitudinally into said chamber and to deposit the same onto saidhearth along one side of said chamber, and means to support said objectsand to move said objects longitudinally out of said casing along theother side thereofu 9. Apparatus of the character described comprisingin combination a casing having a heating chamber therein, means to heatsaid chamber uniformly throughout its length, a continuously movinghearth operative to move elongated objects laterally from one side ofsaid chamber to the other side thereof means to move said elongatedobjects longitu ally into said chamber and to deposit the same onto saidhearth along one sideof said chamber, and means to support said objectsand to move said objects longitudinally out of said chamber along theother side thereof.

ROBERT E. BUCKHOLDT.

